Calculate the size of all cache entries between two points in time.

net/disk_cache/disk_cache.h

Index: net/disk_cache/disk_cache.h
diff --git a/net/disk_cache/disk_cache.h b/net/disk_cache/disk_cache.h
index f71bc81964b929f4dce5596d724c41bf36429279..09924065c4b7bc39be9b031246e9456a0042b888 100644
--- a/net/disk_cache/disk_cache.h
+++ b/net/disk_cache/disk_cache.h
@@ -19,6 +19,7 @@
 #include "base/time/time.h"
 #include "net/base/cache_type.h"
 #include "net/base/completion_callback.h"
+#include "net/base/net_errors.h"
 #include "net/base/net_export.h"
 
 namespace base {
@@ -149,8 +150,19 @@ class NET_EXPORT Backend {
   // Calculate the total size of the cache. The return value is the size in
   // bytes or a net error code. If this method returns ERR_IO_PENDING,
   // the |callback| will be invoked when the operation completes.
-  virtual int CalculateSizeOfAllEntries(
-      const CompletionCallback& callback) = 0;
+  virtual int CalculateSizeOfAllEntries(const CompletionCallback& callback) = 0;
+
+  // Calculate the size of all cache entries accessed between |initial_time| and
+  // |end_time|.
+  // The return value is the size in bytes or a net error code. The default
+  // implementation returns ERR_NOT_IMPLEMENTED and should only be overwritten
+  // if there is an efficient way for the backend to determine the size for a
+  // subset of the cache without reading the whole cache from disk.
+  // If this method returns ERR_IO_PENDING, the |callback| will be invoked when
+  // the operation completes.
+  virtual int CalculateSizeOfEntriesBetween(base::Time initial_time,
+                                            base::Time end_time,
+                                            const CompletionCallback& callback);
 
   // Returns an iterator which will enumerate all entries of the cache in an
   // undefined order.